There are two critical aspects of effectively connecting a computer component such as a printed circuit board to a computer system. First, a circuit board must be correctly electrically connected and grounded. Second and concurrently, the circuit board must be securely mechanically connected. For the sake of efficiency and the reduction of the number of required assembly parts, electrical grounding connection and mechanical connection have commonly been accomplished with the same assembly parts. A typical printed circuit board electrically grounded and mechanically connected within a computer system is a motherboard.
Electrical grounding of a computer chassis and the circuit boards within the chassis is essential to the optimal operation of a computer system. Grounding of an individual circuit board within the computer system allows a ground conductor material within a circuit board to block the electromagnetic interference (EMI) generated by the circuit board from interfering with other circuit boards within the computer system. A ground conductor is formed into a circuit board during circuit board fabrication. The ground conductor is a conductive element that extends across a planar portion of the circuit board. The ground conductor serves to electrically decouple EMI or cross-talk between electric devices on opposing sides of the ground conductor. By including a ground conductor in the circuit boards of a computer system, EMI among circuit boards can be reduced. In order for a ground conductor within a circuit board to be effective, the circuit board must be well connected to a ground source.
A typical ground source for a computer system is the ground supply of a building's electrical grid. The building's ground source is usually accessed through a standard wall socket. A computer power cord provides an electrical connection between the ground supply and the computer system. A ground wire of the power cord is in turn connected to the computer chassis of the computer system. Grounding of the computer circuit boards is accomplished by making an electrical connection between each circuit board and the computer chassis.
Additionally, grounding of the entire chassis provides protection to the circuit boards within the chassis. The grounded chassis not only protects a user from shock when touching a chassis energized by a short circuit, but also shields the circuit boards within the grounded chassis from EMI generated by external sources. In addition, the grounded chassis reduces electromagnetic emissions created by the computer circuit boards from interfering with other electrical devices located around the computer system by blocking those emissions.
Generally, mechanical connection of a computer circuit board to a computer chassis is designed to accomplish two goals. First, the connection should be adequately secure to prevent the circuit board from becoming dislodged under anticipated mechanical service loads. Second, the means for making the connection should be easily operable so that the circuit board may be efficiently installed in the computer system upon initial manufacture and so that removal and replacement of the circuit boards for the purpose of maintenance can be accomplished with reduced effort.
A conventional method of attaching computer circuit boards includes the use of screws. A screw can be placed through a hole in the circuit board, and thereby secure the circuit board to a part of a chassis. This type of connection also provides electrical connection when the screw urges a conductive surface of the circuit board onto a conductive part of the chassis. Connection with screws is not, however, considered an optimal method of connection. Screws require relatively large amounts of time to install and remove. A loose screw that is misplaced within a computer chassis can cause great damage to the circuit boards by shorting between circuits not intended to make electrical contact. Additionally, if a screw is misdirected by an installer and the screw is forced against a portion of the circuit board, damage to the circuit board may be caused.
It is efficient for the manufacturer of computer systems to standardize the manufacturing process to the greatest extent possible while still meeting customer demands. An area where it is particularly advantageous to achieve standardization is in the production of computer chassises and cases. It is a goal in the design of computer chassises that the chassises be able to accommodate as many different varieties of circuit boards as possible with a minimum amount of refitting. Circuit boards for a computer may be merely bought and assembled by a computer manufacturer. Alternatively, the circuit boards may be manufactured by or specially made for a computer manufacturer who then assembles the parts into a computer system. It is advantageous to produce a computer chassis that is capable of receiving standard manufactured circuit boards as well as circuit boards specially manufactured for or by a computer manufacturer.
Many means have been developed by computer manufacturers for effectively electrically grounding and mechanically attaching computer circuit boards such as the motherboard of a computer. Some of these means provide for efficient attachment of a customized motherboard to a chassis without the use of screws as fasteners. However, when standard off-the-shelf motherboards rather than specially manufactured motherboards are used in a computer system, it is conventional in the art to provide a different or modified chassis capable of receiving a standard connection by the use of one or more screws.
An improved device would be capable of electrically connecting a variety of motherboards to a standard chassis. The connection would provide adequate electrical grounding and a secure mechanical attachment. When used with some types of specially manufactured motherboards, the connection could be made without the use of screws or other fasteners that require tools to attach or remove. Additionally, the same chassis could be employed with off-the-shelf motherboards. When used with the off-the-self motherboard, screws may be used to connect the motherboard to the standard chassis. By such an arrangement, an improved device would provide both versatility and an enhanced means of operation whenever possible.